New strategies to overcome water limitation in cultivated maize: Results from sub-surface irrigation and silicon fertilization.

The increasing growth of the world's population has established an unprecedented pressure in the availability of fresh water resources, with food production systems consuming over 70% of the world's fresh water withdrawals. Other pressures include climate change effects and the increasing number of semi-arid regions. The present challenges are therefore the maintenance of high production rates with fewer resources, especially in regions where water is becoming less accessible. In this study, we have tested the effect of sub-surface irrigation and silicon fertilization in maize growth with and without water limitation. These solutions have been suggested as effective in drought conditions but an overall study of their effects on the soil water balance and root length density is lacking. We have conducted a pot experiment with maize for 101 days where measurements in soil water content and root length were taken. Also, Hydrus 2-D was used to simulate the root water uptake and calculate the water balance. Results show that both sub-surface irrigation and silicon fertilization increase the root system by 21% and 34% respectively in water stress situation. Also, in the case of no water stress, silicon fertilization still induces an increase of 11% in the root development, showing that this solution has positive effects even when the crop is not hydrologically limited. Indeed the root water uptake was higher for the silicon treatment when no water limitation was present (71.6 L), compared to the sub-surface irrigation (62.5 L) and the control (62.3 L). While sub-surface irrigation generally decreased evaporation, the silicon treatment lowered drainage by promoting a better and more efficient root water uptake.

Assessment of promising agricultural management practices.

iSQAPER project - Interactive Soil Quality Assessment in Europe and China for Agricultural Productivity and Environmental Resilience - aims to develop an app to advise farmers on selecting the best Agriculture Management Practice (AMPs) to improve soil quality. For this purpose, a soil quality index has to be developed to account for the changes in soil quality as impacted by the implementation of the AMPs. Some promising AMPs have been suggested over the time to prevent soil degradation. These practices have been randomly adopted by farmers but which practices are most used by farmers and where they are mostly adopted remains unclear. This study is part of the iSQAPER project with the specific aims: 1) map the current distribution of previously selected 18 promising AMPs in several pedo-climatic regions and farming systems located in ten and four study site areas (SSA) along Europe and China, respectively; and 2) identify the soil threats occurring in those areas. In each SSA, farmers using promising AMP's were identified and questionnaires were used to assess farmer's perception on soil threats significance in the area. 138 plots/farms using 18 promising AMPs, were identified in Europe (112) and China (26).Results show that promising AMPs used in Europe are Crop rotation (15%), Manuring & Composting (15%) and Min-till (14%), whereas in China are Manuring & Composting (18%), Residue maintenance (18%) and Integrated pest and disease management (12%). In Europe, soil erosion is the main threat in agricultural Mediterranean areas while soil-borne pests and diseases is more frequent in the SSAs from France and The Netherlands. In China, soil erosion, SOM decline, compaction and poor soil structure are among the most significant. This work provides important information for policy makers and the development of strategies to support and promote agricultural management practices with benefits for soil quality.

Landscape cultivation alters δ³°Si signature in terrestrial ecosystems.

Despite increasing recognition of the relevance of biological cycling for Si cycling in ecosystems and for Si export from soils to fluvial systems, effects of human cultivation on the Si cycle are still relatively understudied. Here we examined stable Si isotope (δ(30)Si) signatures in soil water samples across a temperate land use gradient. We show that - independent of geological and climatological variation - there is a depletion in light isotopes in soil water of intensive croplands and managed grasslands relative to native forests. Furthermore, our data suggest a divergence in δ(30)Si signatures along the land use change gradient, highlighting the imprint of vegetation cover, human cultivation and intensity of disturbance on δ(30)Si patterns, on top of more conventionally acknowledged drivers (i.e. mineralogy and climate).